In vitro solubility of calcium, iron, and zinc in rice bran treated with phytase, cellulase, and protease.

Absorption of minerals is inhibited by phytic acid, fiber, and protein because of the chelates formed. Response surface method (RSM) was used in this study to evaluate the effect of application of commercial phytase, protease, and cellulase in rice bran on the in vitro solubility of calcium (IVCa), iron (IVFe), and zinc (IVZn). It is shown that IVCa and IVZn were significantly improved by the application of phytase and cellulase, and the models of two second-order polynomials are recommended for prediction, with coefficients at R(2) = 0.86 and R(2) = 0.88, respectively. Interaction between protease and cellulase also significantly affected IVCa and IVZn. Cellulase had more efficiency than phytase on IVCa. Differing in its effect on Ca and Zn, phytase had a significant linear correlation with IVFe, and none of the other processing parameters exerted a significant effect. The largest increment for IVFe, IVCa, and IVZn occurred in the treatment with applications of phytase at 2.5 U g(-1) and protease and cellulase at 0.2% and 1%, respectively, which were 3.3, 3.6, and 4.3 times, respectively, that of the untreated material.